Question

The user drags the game piece (the i-th image view) to its target location. The program counts, sees that all the items are in the correct places, announces “Game Over” and sets userInteractionEnabled to NO.

Great, except that if the user’s finger is still down on the game piece, the user can drag the piece back out of the target area by accident. “Game Over” is showing but the piece is no longer in the correct place.

Is there a way to force a touchesEnded (not detect a touchesEnded) so that the contact with the game piece is (effectively) broken when the piece is in its final destination (i.e. so that the user can’t accidentally pull it out of position)?

userInteractionEnabled = NO does not seem to take effect until the touch is released.

Answer 1

I’m not aware of a way to force touchesEnded.

Obviously one way to handle this is for your application to maintain state that indicates that the game is over and guard against moving any game pieces when in that state.

You might try beginIgnoringInteractionEvents, though I doubt this will do what you are looking for. I really think managing state in your application that ensures that you will do the right thing, not moving the piece once the end state has been reached, is the way to go.

From Apple’s Event Handling Guide for iOS:

Turning off delivery of touch events for a period. An application can
call the UIApplication method beginIgnoringInteractionEvents and later
call the endIgnoringInteractionEvents method. The first method stops
the application from receiving touch events entirely; the second
method is called to resume the receipt of such events. You sometimes
want to turn off event delivery while your code is performing
animations.